Bourdais: More to come from revised STR

The 30-year-old was just outside the top ten in Friday afternoon's second free practice session, and is confident that the team could still find as much as half a second.

"The car has a lot more than we have shown so far," said Bourdais. "We did not have the best afternoon - I had a problem that stopped us from getting some real reads on the car.

"There are probably four or five tenths to come. Hopefully we can have a good morning so that we can get the right set-up on the car for qualifying."

Bourdais believes that the extra downforce offered by the new wing package makes the car more suited to his driving style having struggled to adapt to the STR4 in the first four races of the season.

"The more downforce you have, the more stable the car becomes," he said. "It's definitely helping. It's calmed the rear down a bit, it's easier to pick up the throttle and it's easier to attack the corners, especially on option tyres.

"But again, I really feel quite bad because on the first lap on options, both times we didn't have the front wing in the car and by the time you adjust, the tyres are gone."

Despite being impressed with the step forward the car has made, the four-time Champ Car champion admitted that he is disappointed not to be closer to sister team Red Bull.

"It makes you feel bad to compare to a team that is a winning contender week-in, week-out," he said. "It's a car that looks very much the same, but which is not completely the same.

"I thought we were going to get really close this weekend, but we're not as close as we wanted to be even though a new front wing and rear wing seems to be a big improvement."

Bourdais added that it is not impossible to make the final session of qualifying, although admitted that it will have to be a perfect lap to get into Q3.

"Q3 is within reach, but we're going to have to put it all together and get it right."